sort.java

hsqldb是100％java实现的数据库,是一个开放源代码的JAVA数据库 l 具有标准的SQL语法和JAVA接口 l HSQLDB可以自由使用和分发 l 非常简洁和快速的

/* Copyright (c) 1995-2000, The Hypersonic SQL Group.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the Hypersonic SQL Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE HYPERSONIC SQL GROUP,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals 
 * on behalf of the Hypersonic SQL Group.
 *
 *
 * For work added by the HSQL Development Group:
 *
 * Copyright (c) 2001-2005, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


package org.hsqldb.lib;

public class Sort {

    /**
     * FastQSorts the [l,r] partition (inclusive) of the specfied array of
     * Rows, using the comparator.
     *
     * Modified from the original method in Hypersonic with the addition of
     * the comparator. (fredt@users)
     *
     * @author Thomas Mueller (Hypersonic SQL Group)
     * @version 1.7.2
     * @since 1.7.2
     */
    public static final void sort(Object[] w, ObjectComparator comparator,
                                  int l, int r) {

        int    i;
        int    j;
        Object p;

        if (l > r) {
            return;
        }

        while (r - l > 10) {
            i = (r + l) >> 1;

            if (comparator.compare(w[l], w[r]) > 0) {
                swap(w, l, r);
            }

            if (comparator.compare(w[i], w[l]) < 0) {
                swap(w, l, i);
            } else if (comparator.compare(w[i], w[r]) > 0) {
                swap(w, i, r);
            }

            j = r - 1;

            swap(w, i, j);

            p = w[j];
            i = l;

            while (true) {
                while (comparator.compare(w[++i], p) < 0) {
                    ;
                }

                while (comparator.compare(w[--j], p) > 0) {
                    ;
                }

                if (i >= j) {
                    break;
                }

                swap(w, i, j);
            }

            swap(w, i, r - 1);
            sort(w, comparator, l, i - 1);

            l = i + 1;
        }

        for (i = l + 1; i <= r; i++) {
            Object t = w[i];

            for (j = i - 1; j >= l && comparator.compare(w[j], t) > 0; j--) {
                w[j + 1] = w[j];
            }

            w[j + 1] = t;
        }
    }

    /**
     * Swaps the a'th and b'th elements of the specified Row array.
     */
    private static void swap(Object[] w, int a, int b) {

        Object t = w[a];

        w[a] = w[b];
        w[b] = t;
    }

    public static class StringComparator implements ObjectComparator {

        public int compare(Object a, Object b) {

            // handle nulls
            if (a == b) {
                return 0;
            }

            if (a == null) {
                return -1;
            }

            if (b == null) {
                return 1;
            }

            return ((String) a).compareTo((String) b);
        }
    }
}